Internal combustion engine manufacturers are constantly seeking to increase power output and fuel efficiency of their products. One method of generally increasing efficiency and power is to reduce the oscillating mass of an engine, e.g., of the pistons, connecting rods, and other moving parts of the engine. Efforts to increase engine power and/or efficiency also may also result in an increase in pressure and/or temperature within the combustion chamber during operation.
Plasma coating process may be used to coat bearing surfaces in internal combustion engines with an alloy by carrying out arc wire spraying. Known arc wire spraying processes include a twin-wire arc spray (TWAS) process, in which two wires are fed to a spray head in such a manner that the electric current is transmitted across the wires. In other examples, a plasma transferred wire arc (PTWA) process may be employed. A PTWA method generally establishes an operating plasma in which a cathode is provided, and a free end of a single consumable wire is melted such that a stream of molten metal particles is continuously fed and projected onto the target surface.
In many extremely demanding applications, present-day internal combustion pistons are made from steel. Pin bore surfaces may tend to scuff as a result of metal to metal contact within the pin bore and the piston pin system. Insufficient lubrication volume and high operating stresses are a direct cause of surface scuffing.
The lack of sufficient lubrication and high service loads on engine parts combine to create extremely high stresses on those parts. Materials that provide better scuff resistance, e.g., than steel, would be desired to extend the service life of the engine. Accordingly, in some applications bushings are provided as an interface between pin bore surfaces and the piston pin. However, such bushings add cost, complexity, and weight to the piston assembly.
Accordingly, there is a need for a piston that addresses the above problems.